Faculty Bibliography

STUDY OBJECTIVES: To evaluate epoch by epoch agreement in sleep stage assignment between scorers from different laboratories. DESIGN: N/A. METHODS: 62 NPSGs were selected for analysis from 3 sleep centers (38 diagnostic studies for sleep disordered breathing [SDB], 10 studies during CPAP titration, and 14 studies in subjects with no sleep related complaints or sleep pathology). The sleep recording montage consisted of at least 2 EEG leads, left and right EOG and a submental EMG. Scoring was performed manually by 5 experienced sleep technologists. No scorer had knowledge of any other scorers' results. Agreement was tabulated both for sleep stage distribution and on an epoch by epoch basis for the entire data set and the normal and SDB subsets. MEASUREMENTS AND RESULTS: The mean epoch by epoch agreement between scorers for all records was 73% (range 67-82%). Agreements were higher in the normal subset (mean 76%, range 65-85%) than in the SDB subset (mean 71%, range 65-78%). There was significant variability in agreement between records and between pairs of scorers. Overall, 75% of epochs had at least 4 of the 5 scorers in agreement on the sleep stage and 96% of epochs had agreement of at least 3 of the 5 scorers. CONCLUSIONS: The level of agreement in sleep stage assignment varies between scorers, by diagnosis, and by record. The level of agreement between laboratories is lower than what can be maintained between scorers within the same laboratory. This warrants caution when comparing data scored in separate laboratories. The lower agreement in SDB patients supports the generally held view that sleep fragmentation makes application of the R&K rules less reliable

STUDY OBJECTIVES: The published AASM guidelines approve use of a nasal cannula/pressure transducer to detect apneas/hypopneas, but require esophageal manometry for Respiratory Effort-Related Arousals (RERAs). However, esophageal manometry may be poorly tolerated by many subjects. We have shown that the shape of the inspiratory flow signal from a nasal cannula identifies flow limitation and elevated upper-airway resistance. This study tests the hypothesis that detection of flow limitation events using the nasal cannula provides a non-invasive means to identify RERAs. DESIGN: N/A SETTING: N/A PATIENTS: 10 UARS/OSAS and 5 normal subjects INTERVENTIONS: N/A MEASUREMENTS AND RESULTS: All subjects underwent full NPSG. Two scorers identified events from the nasal cannula signal as apneas, hypopneas, and flow limitation events. Two additional scorers identified events from esophageal manometry. Arousals were scored in a separate pass. Interscorer reliability and intersignal agreement were assessed both without and with regard to arousal. The total number of respiratory events identified by the two scorers of the nasal cannula was similar with an Intraclass Correlation (ICC) =0.96, and was essentially identical to the agreement for the two scorers of esophageal manometry (ICC=0.96). There was good agreement between the number of events detected by the two techniques with a slight bias towards the nasal cannula (4.5 events/hr). There was no statistically significant difference (bias 0.9/hr, 95%CI -0.3-2.0) between the number of nasal cannula flow limitation events terminated by arousal and manometry events terminated by arousal (RERAs). CONCLUSION: The nasal cannula/pressure transducer provides a non-invasive reproducible detector of all events in sleep disordered breathing; in particular, it detects the same events as esophageal manometry (RERAs)

OBJECTIVES: To evaluate study failure and sensor loss in unattended home polysomnography and their relationship to age, gender, obesity, and severity of sleep-disordered breathing (SDB). DESIGN: A cross-sectional analysis of data gathered prospectively for the Sleep Heart Health Study (SHHS). SETTING: Unattended polysomnography was performed in participants' homes by the staff of the sites that are involved in SHHS. PARTICIPANTS: 6,802 individuals who met the inclusion criteria (age >40 years, no history of treatment of sleep apnea, no tracheostomy, no current home oxygen therapy) for SHHS. RESULTS: A total of 6802 participants had 7151 studies performed. 6161 of 6802 initial studies (90.6%) were acceptable. Obesity was associated with a decreased likelihood of a successful initial study. After one or more attempts, 6440 participants (94.7%) had studies that were judged as acceptable. The mean duration of scorable signals for specific channels ranged from 5.7 to 6.8 hours. The magnitudes of the effects of age, gender, BMI, and RDI on specific signal durations were not clinically significant. CONCLUSION: Unattended home PSG as performed for SHHS was usually successful. Participant characteristics had very weak associations with duration of scorable signal. This study suggests that unattended home PSG, when performed with proper protocols and quality controls, has reasonable success rates and signal quality for the evaluation of SDB in clinical and research settings

Objective: This is one of two separate clinical trials to evaluate the efficacy and safety of modafinil, a novel wake-promoting agent, inpatients with excessive daytime sleepiness (EDS) associated with narcolepsy. Methods: In this 9-week, randomized, placebo-controlled, double-blind, 21-center clinical trial, patients were randomized to receive fixed daily doses of modafinil 200 mg, modafinil 400 mg, or placebo. A placebo-controlled, 8-week treatment discontinuation phase was included to evaluate the effects of withdrawal on patients who had been receiving modafinil. A total of 271 patients who were naive to modafinil received study medication:in the 9-week trial and 240 patients received;study medication in the discontinuation phase. Results: Treatment with modafinil resulted in significant improvement in two objective measures of E

Varying approaches to measuring the respiratory disturbance index (RDI) may lead to discrepant estimates of the severity of sleep-disordered breathing (SDB). In this study, we assessed the impact of varying the use of corroborative data (presence and degree of desaturation and/or arousal) to identify hypopneas and apneas. The relationships among 10 RDIs defined by various definitions of apneas and hypopneas were assessed in 5,046 participants in the Sleep Heart Health Study (SHHS) who underwent overnight unattended 12-channel polysomnography (PSG). The magnitude of the median RDI varied 10-fold (i.e., 29.3 when the RDI was based on events identified on the basis of flow or volume amplitude criteria alone to 2.0 for an RDI that required an associated 5% desaturation with events). The correlation between RDIs based on different definitions ranged from 0.99 to 0.68. The highest correlations were among RDIs that required apneas and hypopneas to be associated with some level of desaturation. Lower correlations were observed between RDIs that required desaturation as compared with RDIs defined on the basis of amplitude criteria alone or associated arousal. These data suggest that different approaches for measuring the RDI may contribute to substantial variability in identification and classification of the disorder

The contribution of apnea to chronic hypercapnia in obstructive sleep apnea (OSA) has not been clarified. Using a model (D. M. Rapoport, R. G. Norman, and R. M. Goldring. J. Appl. Physiol. 75: 2302-2309, 1993), we previously illustrated failure of CO(2) homeostasis during periodic breathing resulting from temporal dissociation between ventilation and perfusion ('temporal V/Q mismatch'). This study measures acute kinetics of CO(2) during periodic breathing and addresses interapnea ventilatory compensation for maintenance of CO(2) homeostasis in 11 patients with OSA during daytime sleep (37-171 min). Ventilation and expiratory CO(2) and O(2) fractions were measured on a breath-by-breath basis by means of a tight-fitting full facemask. Calculations included CO(2) excretion, metabolic CO(2) production, and CO(2) balance (metabolic CO(2) production - exhaled CO(2)). CO(2) balance was tabulated for each apnea/hypopnea event-interevent cycle and as a cumulative value during sleep. Cumulative CO(2) balance varied (-3,570 to +1,388 ml). Positive cumulative CO(2) balance occurred in the absence of overall hypoventilation during sleep. For each cycle, positive CO(2) balance occurred despite increased interevent ventilation to rates as high as 45 l/min. This failure of CO(2) homeostasis was dependent on the event-to-interevent duration ratio. The results demonstrate that 1) periodic breathing provides a mechanism for acute hypercapnia in OSA, 2) acute hypercapnia during periodic breathing may occur without a decrease in average minute ventilation, supporting the presence of temporal V/Q mismatch, as predicted from our model, and 3) compensation for CO(2) accumulation during apnea/hypopnea may be limited by the duration of the interevent interval. The relationship of this acute hypercapnia to sustained chronic hypercapnia in OSA remains to be further explored

STUDY OBJECTIVES: We addressed the issue of how commuting affects sleep habits, and its association with general health and potential sleep disorders in individuals on a large, U.S. commuter rail system. DESIGN: Postage-paid mail back questionnaires were distributed to commuters over 6 consecutive weekdays. The questionnaire incorporated previously validated questions regarding sleep habits. SETTING: Questionnaires were dispensed at 15 different rail stations. PARTICIPANTS: 21,000 commuters accepted the questionnaire. MEASUREMENTS AND RESULTS: Data was analyzed by total group and length of commute. A total of 4715 (22%) questionnaires were returned. Over 50% of the sample reported difficulty with sleep and wakefulness while only 3% sought professional help. Sleep apnea was suspected in 4.2% of male and 1% of female respondents and was associated with increased reports of excessive daytime sleepiness, and history of hypertension, diabetes and obesity. Total nocturnal sleep time was significantly less in those subjects with long commutes. Seventy percent of respondents reported napping during the commute. Length of commute was associated with hypertension. CONCLUSION: Commuting long distances negatively impacts one's ability to capture adequate sleep. Data suggests that there may be significant numbers of respondents with unrecognized sleep disorders which further impact on general health

Therapeutic decisions in patients with sleep apnea (eg, adjustment of continuous positive airway pressure [CPAP]) depend on differentiating central from obstructive apnea. Obstructive apnea is defined by cessation of airflow in the presence of continued respiratory effort, which is conventionally inferred from chest wall movement or intrathoracic pressure swings. Cardiogenic oscillations in the airflow have been observed during some central apneas, but there is controversy over whether they correlate with airway patency. The present study investigates whether these oscillations are markers of the absence of respiratory effort (central apnea) without regard to airway patency. METHODS: We examined 648 apneas in 52 patients undergoing nocturnal polysomnograms and CPAP titrations. Airflow was measured using the output of the CPAP generator, and apneas were identified from reduction of airflow to < 10% for > 10 s. We used only the presence or complete absence of thoracoabdominal motion to classify apneas: obstructive apnea when motion was present (297 apneas); and central apnea if motion was totally absent (351 apneas). Central apneas most often occurred at sleep onset or followed arousal with a big breath. Using only the flow signal, all apneas were examined for the presence of cardiogenic oscillation by an observer blinded to other signals and apnea types. RESULTS: No obstructive apnea showed definite cardiogenic oscillations. In four cases, there was a suggestion of oscillation that was not regular enough to be called cardiac. Sixty percent of central apneas showed clear, regular oscillations at cardiac frequency. Cardiogenic oscillations also were seen intermittently during quiet exhalation in apnea-free periods. CONCLUSION: The presence of cardiogenic oscillations on the CPAP flow signal is a specific indicator of central apnea and may have a role in self-titrating CPAP algorithms. We speculate that transmission of these cardiac-induced oscillations may relate to the relaxation of thoracic muscles during central apnea and is impeded by high muscle tone during obstructive apnea